This is a family of about four hundred species with
small to medium sized shells, distributed world-wide, common in the
tropics but also in temperate Australia. They occur from the intertidal
down to at least 1000 m deep. The family is close to the Buccinidae
anatomically, being differentiated by radular features and differences in
the alimentary and reproductive systems.

Columbellids are active, crawling snails that live
in a variety of habitats. The majority of species live on hard
substrates, crawling on the underside of stones or on algae, but some
species crawl in sand in seagrass beds. They are unusual among advanced
gastropods in that a few species include both plant and animal material
in their diets. Species that live on seagrass are grazers, consuming the
diatoms, sponges and other animal life forms on the seagrass fronds,
while also consuming the plant material. Carnivorous species are known to
include other molluscs, polychaete worms, crustaceans and ascidians in
their diet.

The family is marked by great variability, both between
and within species. Shell form varies from biconic and ovate shapes typical of the Buccinidae to elongate shapes more typical of the
Mitridae and Turridae. Within some groups, particularly the southern Mitrella
species,
there is extreme variation of colour pattern from uniformly pale to
uniformly dark with a wide array of stripes and spots in between. In the
minute species Anachis atkinsoni shell form and pattern is so
variable that it is difficult to believe that only one species is
present.

The classification within the family suffers from a lack of overall synthesis. Radwin (1977a, 1977b, 1978) has studied the
Atlantic species. The larger Indo-West Pacific species are relatively
well known, but the southern Australian fauna, particularly the
deep-water species, are known only from empty shells and have been
assigned to genera without adequate justification. DeMaintenon (1999)
has presented a phylogenetic analysis based on 23 species but did not
include most of the genera of interest in southern Australia.

The NSW fauna contains representatives of tropical
Indo-West Pacific groups, a southern Australian endemic group, deep
water species, and one introduced species. Common tropical species of Euplica and Mitrella
occur in northern NSW, sometimes reaching further south to be uncommon
at Sydney. The endemic southern Australian group consists of nine
species, eight of which occur in NSW. Three
of the species - Mitrella australis, M. tayloriana and M.
intexta - are almost restricted to NSW, with M. tayloriana
being the most common columbellid in the state, and a prominent member
of the intertidal algal fauna. The species Mitrella bicincta has
been introduced from east Asia, and is now common in central NSW. In
addition to the intertidal and shallow water species, there are
continental shelf and slope species that occur down to at least 1000 m
deep.

Family References

On a world-wide basis there has been no revision of
the family, and no consolidated reference since Reeve's Conchologia
Iconica in the mid-19th century. Wilson (1994) gives a compilation
of the Australian species, but this is severely limited by the
inadequate knowledge of the family. There has been no revision or
comprehensive reference to the NSW species.

Coverage

All the named species from NSW are detailed here.
There seems to be about 10 additional unnamed species occurring in the
waters of the state. Most are deep water; two or three are similar
to Aesopus plurisulcatus; another, from around 1000 m deep
resembles Mitrella; and a few minute species are close to Retizafra.
The following species are listed as occurring in NSW by Iredale &
McMichael (1962), but no NSW specimens can be found in the Australian
Museum collection: Mitrella abyssicola (Brazier, 1877); Mitrella
ligula (Duclos, 1840); Mitrella puella (Sowerby, 1844). The
name Mitrella alizonae (Melvill & Standen, 1901) was used by
Iredale & McMichael, but it is an
incorrect identification for one of the deep water, undescribed species.

Identification Notes

Shell form and sculpture in this family is
extremely variable. Shape varies from short and squat to elongate.
Sculpture may be smooth, axially ribbed, spirally corded, or both, but a
constant feature is spiral cords on the base. Shells show the overall
features of the highly evolved gastropods, most noticeably a siphonal
canal, in common with families such as Buccinidae, Nassariidae and Turridae.
The specific shell features which assist in placement into the
Columbellidae are:

There is a very short siphonal canal, often little
more than a gap at the anterior end of the aperture.

Outer lip sinus: there is a sinus, or gap, in
the top of the outer lip, a feature also found in the Turridae. In
the Columbellidae it is usually shallow, but much deeper in the
Turridae.

Outer lip dentition: there are usually denticles
inside the outer lip, although some species have just a single
indistinct bulge. The strength of the denticles varies from species
to species, and with growth stage of the shell. In some species the
denticles are only developed in the most mature specimens, therefore
only
being seen in a small percentage of shells.

Inner (columellar) lip dentition: the inner lip
of the aperture is without plaits, providing a point of separation
from Marginellidae, Mitridae, and Volutidae. There are often weak
denticles on the inner lip, aligned on an axial ridge just inside
the edge of the callus, but these also tend to be restricted to
mature shells.